The presence of $Mn$ in steel produces

$Cr_2O_7^{2-} / H^{\oplus}$ $\xrightarrow[200^{\circ}C]{H_2O_2} 'X'$ $\xrightarrow{\text{On Standing}} 'Y'_{(aq. sol)}$
Select the correct option for $'X'$ and $'Y'$

$KMnO_4$ decomposes on heating at $513 \ K$ to form $O_2$ along with

The oxoanion in which the oxidation state of the central atom is same as its group number in the periodic table is

Write about the utility of $d$- and $f$-block elements and their compounds. Or describe the following uses of $d$- and $f$-block elements and their compounds: $(i)$ In iron/steel $(ii)$ As pigments $(iii)$ In batteries $(iv)$ In coinage $(v)$ As catalysts.

Which of the following statements is true regarding the structure of $Cr_2O_7^{2-}$?